1. Field of the Invention
The present invention relates to semiconductor devices and a method of manufacturing same. More particularly, the invention relates to a method of manufacturing a capacitor dielectric layer for use in a semiconductor device having improved leakage current characteristics.
2. Description of the Related Art
In recent years, the demand for densely integrated, high-performance semiconductor devices has remained unabated. In the context of semiconductor memory devices, these demand drivers implicate the design and fabrication of the capacitor constituent to each memory cell. Among the other components forming the individual memory cells of a semiconductor memory device, the size of the capacitor tends to dominate the design and particular attention must be paid to the capacitance per unit area occupied by the capacitor. That is, even though the size of the capacitor has been decreased, its capacitance must remain sufficiently high to ensure proper operation of the device, while its breakdown voltage must also remain sufficiently high to ensure device reliability. One approach to maximizing capacitance of a capacitor having a reduced physical size focuses on the dielectric material separating the capacitor's lower electrode from its upper electrode.
Following recent developments along this line, when a single zirconium oxide layer (ZrO2) is used as a capacitor dielectric layer in an MIM capacitor, its equivalent oxide thickness (hereinafter, referred to as “Toxeq”) is excellent, but its leakage current characteristics are poor. (The equivalent oxide thickness, Toxeq, is a comparative metric for a dielectric layer expressed in terms of silicon oxide, i.e., a metric stating an equivalent thickness of silicon oxide necessary to provide the same capacitance).
Accordingly, high dielectric layers having a composite material structure, such as a ZrO2 and aluminum oxide layer (Al2O3) or “ZAZ layer”, have been proposed. Unfortunately, such composite material layers are generally thicker than a single ZrO2 dielectric layer. This increased thickness of the dielectric layer is at odds with ongoing design imperatives to reduce the overall size of constituent components including the capacitor.